Root feeding devices are used in the irrigating and fertilizing of root systems for trees and plants having roots an appreciable distance below the ground surface. Where the nozzle unit of the feeding device has a uniform outer diameter the outlets of radially extended passages tend to become clogged and the fluid discharged therefrom during the irrigation or fertilization period tends to follow linear paths radially of the nozzle unit. Nozzle units of this general type are disclosed in U.S. Pat. Nos. 2,505,174; 3,618,539; 2,302,799; 1,650,081; 2,242,789; and 2,214,083. In U.S. Pat. No. 3,397,541, the nozzle unit functions as a control valve providing only an axial flow of fluid while being inserted, and then, upon partial retraction of the nozzle unit, a radial or fan type flow of fluid. Softening and lubrication of the soil is accomplished solely by the axial flow of fluid, unless the device is manipulated to provide additional lubrication by the radial flow.
Lawn soil generally found in the area of the home yard or in an urban or suburban setting consists of minerals, organic matter and, particularly in the case of lawns, of a multitude of roots of various sizes. In the usual method of insertion of the nozzle tip of a feeding device into the soil, the tip acts as a wedge to push the soil away from the tip supporting tube. In the case of dry or loose soil, this pushing or spreading action may force cracks or fractures in the soil structure. As the water is ejected from the nozzle, and particularly in dry or hard soil, the water is often directed vertically upwardly about the tube since it tends to follow the path of least resistance, rather than spreading laterally outward into the hard or dry soil. The nozzle structure of the invention softens and moistens the soil in the vicinity of the nozzle tip to increase its compressibility. The subsequent wedge action of the nozzle tip forms a seal around the tube which acts to direct the water laterally around the nozzle structure to substantially reduce the vertical back up of the water toward the ground surface.